A typical control cable is formed by a flexible pipe-shaped outer casing and an inner cable made of a metal wire, with the inner cable being inserted through the outer casing. The control cable has a remote control function by pushing, pulling, or rotating one end of the control cable to realize remote control of a passive type device disposed at the other end of the control cable. For example, the control cable may be used in a vehicle for various purposes, such as an open/close cable for a sunroof, an open/close cable for windows, or a cable for the parking break.
For an outer casing of the control cable, dimensional stability in a longitudinal direction is strictly required. Since the inner cable is a metal wire, a linear expansion coefficient and a compression characteristic equivalent to those of the metal wire are required.
If thermal expansion of the outer casing is large, the inner cable acts as if pulled even when the inner cable is not operated. This may cause a malfunction such as failure to close an oil supply port. If the outer casing is soft, the length of the outer casing may be compressed and shortened by operation of the inner cable. In such a case, the control cable may be inoperable even when the inner cable is pulled.
Such things can be confirmed by measuring a thermal expansion and stroke loss (play of the inner cable that causes malfunction if it is too large) of resin of the outer casing. Specifically, stroke loss is measured by measuring stroke values relative to a load acted on the inner cable by changing temperatures. A lower value of stroke loss is preferable.
The outer casing made of resin tends to generate problems as described above. A tubular body, therefore, that is formed by tightly winding a flat steel wire around the outer periphery of an inner tube (liner) made of resin in a spiral manner, with the outer side of the tubular body further covered by resin has conventionally been used (see Japanese Patent Application Laid-Open No. 2002-286017, for example).
However, such an outer casing around which the flat steel wire is spirally and tightly wound is heavy, and does not satisfy lightweight requirement in the recent trend of electric vehicles or hybrid vehicles.
Meanwhile, an outer casing in which a metal wire is linearly buried in a resin layer has been proposed (see JP-A Nos. S47-11410, S59-16726, and 2011-99524, and Japanese Utility Model Application Laid-Open No. 59-22322, for example).
For example, an outer casing for a control cable in which a reinforcing wire, in which flat portions are formed by pressing a metal tube at appropriate intervals, is buried in parallel with an axial center of the casing body in the thickness of the tubular casing body made of synthetic resin has been proposed (see JP-U No. S59-22322).
A method of manufacturing an outer casing by introducing a metal wire into an extruder and burying the metal wire in a thickness part of the tubular conduit made of resin has also been proposed (see JP-A No. S59-16726, for example).
A control cable used in a drain plug remote operation apparatus, which has an outer casing including two metal wires buried in a cylindrical body made of polyolefin-based thermoplastic elastomer in parallel with the axis of the body and opposing from each other by 180 degrees about the axis has also been proposed (see JP-A 2011-99524).